I had a mini-scoop on Google's mystery barge, which has since been described by the company as a floating events space to showcase new technology:

Google has held initial discussions with San Francisco’s Fort Mason Center to dock its mysterious barge on a pier there, The Verge has confirmed. "They’re in discussions on the idea of mooring a floating barge off of one of the piers at Fort Mason for a period of time," said Howard Levitt, director of communications and partnerships at Golden Gate National Recreation Area, which manages Fort Mason. "The details, we’re still trying to ascertain ourselves."